PALO ALTO, CA - March 3, 2004 - Varian Medical Systems, Inc. (NYSE: VAR) today announced it has received FDA 510(k) clearance of its On-Board Imager accessory for the company's Clinac® and Trilogy™ medical linear accelerators. The new imaging accessory is designed to improve the precision and effectiveness of cancer treatments by giving doctors the ability to target and track tumors more accurately.

"Our new automated system for image-guided radiation therapy (IGRT) will enable clinicians to obtain high-resolution X-ray images to pinpoint tumor sites, adjust patient positioning when necessary, and complete a treatment, all within the standard treatment time slot," said Timothy Guertin, president of the company's Oncology Systems business.

Up to now, radiation oncologists have had to contend with variations in patient positioning and with respiratory motion by treating a margin of healthy tissue around the tumor. IGRT enables doctors to locate the tumor while the patient is in the treatment position, and to minimize the volume of healthy tissue exposed to radiation during treatment.

Robotic Technology
Varian's On-Board Imager is mounted on the treatment machine via robotically controlled arms which operate along three axes of motion, so that they can be positioned optimally for the best possible view of the tumor.

An amorphous silicon flat-panel X-ray image detector yields digital images showing internal anatomic landmarks with a high degree of precision. In addition, the image detector can track anatomic motion and thus provide doctors with a clear indication of exactly how a tumor will move during treatment due to respiration or other normal physiological processes. Varian has also incorporated a unique 150 kV X-ray tube designed for generating precise, high-resolution CT-quality images from a moving gantry.

"By using our robotic technology and control software to position the On-Board Imager and patient couch, the total system offers the automation, speed, and flexibility needed to make the IGRT process clinically practical for thousands of cancer patients," Guertin noted. The system is designed for full integration with Varian's VARiS Vision™ image and information management system as well as the company's Eclipse™ treatment planning software products.

"Varian's Clinac and Trilogy accelerators, equipped with the new On-Board Imager, will give doctors the best of two critical technologies for image-guided radiation therapy. We have combined two important technologies on one platform-low-dose, high resolution, kilovoltage X-ray imaging and integrated software control of all treatment parameters," said Guertin. "This opens the door to improved, rapid, cost-effective automated treatments that are conducive to patient comfort."

The new On-Board Imager will be available as an option on all of Varian's newly installed high-energy Clinac linear accelerators, and as an upgrade for most digital Clinac accelerators already in place at clinical sites. It will be a standard feature on all Trilogy linear accelerators.

Trilogy
Trilogy, the world's first linear accelerator for stereotactic and other advanced forms of radiotherapy, was introduced as a prototype in October 2003, and received FDA 510(k) clearance in January 2004. Designed to accommodate the On-Board Imager, Trilogy will utilize radiographic, fluoroscopic, and, later this year, 3-D cone-beam CT images.

The Trilogy system can deliver stereotactic radiosurgery and fractionated stereotactic radiation therapy, as well as 3D conformal radiotherapy, SmartBeam IMRT, and Dynamic Targeting IGRT. "Outfitted with the new On-Board Imager, the Trilogy system can handle any cancer case that is treatable with radiation therapy," said Guertin. "It is the most advanced, versatile, and cost-effective device of its kind."